Upcoming ESP32 memory allocation change

[phoddie]

I'm writing to share plans for an upcoming change to the default memory allocation on ESP32 devices.

Today, all devices in the ESP32 family use the same default memory allocation defined in Node-RED MCU Edition. This worked well for some time, especially for the original ESP32, but as the ESP32 family has grown, it is not optimal. There are devices with much more RAM (using PSRAM) and devices with less RAM (ESP32-C3). A single default means that more capable devices cannot take full advantage of their RAM, which less powerful devices may run out of memory sooner than necessary because Node-RED is taking more than its share of memory.

To address this, the default memory allocation in Node-RED MCU Edition for ESP32 devices will be removed. This will cause the default memory allocation from the device host to be used. For the original ESP32 devices, this is about the same (slightly smaller). For devices with PSRAM, it will be much larger. For devices like ESP32-C3, it will be smaller, but the devices won't run out of memory on launch when Wi-Fi and BLE are used together.

Developers using the Node-RED plugin by @ralphwetzel can still override the default memory configuration, so you can use whatever memory configuration your project needs.

This change will go live at about the same time as the next Moddable SDK release, in the first half of August 2025. I recommend updating both Node-RED MCU Edition and the Moddable SDK at the same time. If you have concerns about this change or encounter issues as a result of this change, please report them on this repository.

[phoddie]

The change described above is now live. Be sure to use Moddable SDK 5.10.0 or later with Node-RED MCU Edition.

With a little luck, it will be transparent for most projects.